1. Field of Invention
This invention relates to method and apparatus for lifting tainter gates and, more specifically to an hydraulically powered pin lift mechanism for raising very large tainter gates in waterways, and the like.
2. Description of the Prior Art
Controlling flow through artifical and natural watercourses is a problem that is as old as civilization itself. Usually, this flow control has been imposed through different types of gates. These gates serve as temporary dams or valves that, when closed, impound water in one portion of the watercourse system or, when open, release accumulated water to permit it to flow into other parts of the system.
Tainter (or taintor) gates, which also are often referred to as "radial" gates, are frequently used for this purpose. Basically, a tainter gate has an upstream face that is curved in the form of an arc, the center of which is at the center of the gate hinge. Raising and lowering the curved face of the gate relative to the hinge opens and closes the watercourse to enable water to flow past the gate or to accumulate upstream of the gate, respectively, depending on the particular needs of the watercourse system.
As watercourse dimensions have increased from the small, primitive irrigation ditches that are still found in many parts of the world to the massive channels of more than seventy feet in depth and sixty feet in width encountered in modern civil engineering practice, the apparatus required to control this flow necessarily must change from simple, manually operated gate valves to large, powerful devices capable of manipulating tainter gates weighing tons against hydraulic forces that are, perhaps, equally great or greater.
A number of techniques have gradually developed through the years for coping with the greater forces that characterize these large watercourses. Illustratively, it has been the practice to couple wireropes to the tainter gates. These wireropes are controlled by means of electrical motor-driven, ribbon-wound cable type hoists to open or close the tainter gates, as desired. Reliance on cable control, however, can lead to a number of difficulties. Typical of these problems is the potential for an uneven load distribution among the wireropes that are secured to both sides of the tainter gates. On occasion, moreover, some of the wireropes wound on which drums have been crushed. This crushing occurs because of the high loads that are applied to the wireropes and the large number of wraps or turns of the cable that are wound onto the drums in order to raise a tainter gate more than 100 feet. These wireropes also create large and undesirable torsional moments in the vertical support beam end frame of the tainter gate, as well as creating undesirable circumferential stresses in the tainter gate skin plate. The large number of wireropes required to control more massive tainter gates introduce still further difficulties in properly tensioning the wireropes and synchronizing their action.
Clearly, as tainter gate sizes increase, it appears that a law of diminishing returns may be overtaking the further application of wirerope technology to watercourse control. More cables, greater lift distances, heavier tainter gates and deeper watercourses all seem to combine to produce the further problems considered above. Accordingly, there is a need for an entirely new approach to tainter gate control.
U.S. Pat. No. 2,125,311 granted Aug. 2, 1938 to B. L. Peterson for "Water Supply and Drainage System for Fishlocks" describes a system in which a tainter valve is directly linked to a rack-and-pinion mechanism. Although this approach overcomes many of the difficulties that have beset wirerope apparatus, the force required for direct gate drive may be excessive for more massive tainter gates, or the mechanical advantage is of such a nature that too much time is required to open these larger gates.
U.S. Pat. No. 2,125,090 granted July 26, 1938 to H. E. Smyser for "Rotatable Water Gate" also discloses a direct mechanical connection between the tainter gate and a worm gear that controls the movement of the gate. Although a worm gear is capable of developing suitable forces, once more the mechanical advantage of this particular mechanism is not acceptable for very large tainter gate installations.
U.S. Pat. No. 2,080,063 granted May 11, 1937 to J. J. Ring for "Roller Gate Construction" also fails to suggest a system that is capable of lifting large tainter gates. Thus, as shown in this patent, a rack, secured to a tainter gate pier meshes with a large pinion gear that is formed on the circumference of the gate structure to enable a chain attached to the gate to draw, or roll the gate up along the rack. The chain in this circumstance must sustain the full load of the gate as it is being lifted, thereby imposing unsatisfactorily inordinate power requirements for large gate application.
Consequently, a need continues to exist for a more efficient and reliable means for lifting or otherwise moving large tainter gates.